Recently, mobile terminals equipped with a touch screen are widely used due to convenience of input and a slim shape. The touch screen provides an input and output function. To this end, the touch screen includes a display panel and a touch panel. The touch screen provides the output function through the display panel and provides the input function through the touch panel.
The mobile terminal supporting the touch screen recognizes not only a touch of hand but also a touch input device such as a stylus or a touch pen to provide detailed input. The touch pen is divided into an active type which needs power and a passive type which needs no power. The active type touch pen includes a power supply such as a battery. The active type touch pen operates an LC resonance circuit consisting of an inductor (L) and a capacitor (C) through the power supply. The mobile terminal receives a wireless signal generated in the LC resonance circuit of the touch pen by an antenna having an array shape embedded on the mobile terminal, and recognizes location of the touch pen by using reception strength for each antenna.
The passive type touch pen does not include an additional power supply and receives the power from a mobile terminal to operate by using electromagnetic induction. For example, the passive type touch pen using electromagnetic induction mainly utilizes an Electro Magnetic Resonance (EMR) by using the LC resonance circuit. The passive type touch pen utilizing the EMR by the LC resonance circuit receives a wireless signal from the mobile terminal through the LC resonance circuit and transmits a reflection signal corresponding to the received wireless signal to the mobile terminal. At this time, the mobile terminal receives the reflection signal which is transmitted from the LC resonance circuit of the touch pen by the embedded antenna of array shape, and recognizes location of the touch pen by measuring a reception strength corresponding to each antenna.
In the meantime, the touch pen of the EMR type using the LC resonance circuit provides status information such as a pen pressure, a button input, and the like through variation of a resonance frequency corresponding to the reflection signal. To this end, the related-art touch pen of the EMR type using the LC resonance circuit includes a capacitor, an inductor, a variable inductor, a variable capacitor, and the like in order to change the resonance frequency of the LC resonance circuit according to the pen pressure or the button input.
However, the above described related-art touch pen of the EMR type using the LC resonance circuit provides the status information such as the pen pressure, the button input and the like through only the change of the resonance frequency. Thus, the related-art touch pen of the EMR type using the LC resonance circuit has a limitation in the kind of status information that can be provided to the mobile terminal. In addition, the inductor, the capacitor, the variable inductor, and the variable capacitor used in the related-art touch pen of the EMR type using the LC resonance circuit has not only a large error due to the characteristic of the device but also has a high sensibility in the change of environment such as a temperature. Accordingly, the related-art touch pen of the EMR type using the LC resonance circuit has a problem in that a compensation circuit for compensating the error due to the change of the environment is required.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.